lspdece.c

ITU-T在1996年3月公布了G.729建议的8Kbit/s共轭结构代数码激励线性预测（CS-ACELP）语音编码方案

/*
    ITU-T G.729 Annex I  - Reference C code for fixed point
                         implementation of G.729 Annex I
                         Version 1.1 of October 1999
*/
/*
 File : lspdece.c
 */
/* from lspdece.c G.729 Annex E Version 1.2  Last modified: May 1998 */
/* from lspdec.c G.729 Version 3.3            */

#include "typedef.h"
#include "basic_op.h"
#include "ld8k.h"
#include "ld8cp.h"
#include "tab_ld8k.h"
#include "tabld8cp.h"

/*----------------------------------------------------------------------------
 * Lsp_decw_resete -   set the previous LSP vectors
 *----------------------------------------------------------------------------
 */
void Lsp_decw_resete(
  Word16 freq_prev[MA_NP][M],    /* (o) Q13 : previous LSP MA vector        */
  Word16 prev_lsp[],            /* (o) Q13 : previous LSP vector        */
  Word16 *prev_ma               /* previous MA prediction coef.*/
)
{
    Word16 i;
    
    for(i=0; i<MA_NP; i++)
        Copy( &freq_prev_reset[0], &freq_prev[i][0], M );
    
    *prev_ma = 0;
    
    Copy( freq_prev_reset, prev_lsp, M);
}

/*----------------------------------------------------------------------------
 * Lsp_iqua_cse -  LSP main quantization routine
 *----------------------------------------------------------------------------
 */
void Lsp_iqua_cse(
 Word16 prm[],          /* (i)     : indexes of the selected LSP */
 Word16 lsp_q[],        /* (o) Q13 : Quantized LSP parameters    */
 Word16 erase,           /* (i)     : frame erase information     */
  Word16 freq_prev[MA_NP][M],    /* (i/o) Q13 : previous LSP MA vector        */
  Word16 prev_lsp[],            /* (i/o) Q13 : previous LSP vector        */
  Word16 *prev_ma               /* (i/o) previous MA prediction coef.*/
)
{
    Word16 mode_index;
    Word16 code0;
    Word16 code1;
    Word16 code2;
    Word16 buf[M];     /* Q13 */
    
    if( erase==0 ) {  /* Not frame erasure */
        mode_index = shr(prm[0] ,NC0_B) & (Word16)1;
        code0 = prm[0] & (Word16)(NC0 - 1);
        code1 = shr(prm[1] ,NC1_B) & (Word16)(NC1 - 1);
        code2 = prm[1] & (Word16)(NC1 - 1);
        
        /* compose quantized LSP (lsp_q) from indexes */
        Lsp_get_quante(lspcb1, lspcb2, code0, code1, code2,
            fg[mode_index], freq_prev, lsp_q, fg_sum[mode_index], buf);
        
        /* save parameters to use in case of the frame erased situation */
        Copy(lsp_q, prev_lsp, M);
        *prev_ma = mode_index;
    }
    else {           /* Frame erased */
        /* use previous LSP */
        Copy(prev_lsp, lsp_q, M);
        
        /* update freq_prev */
        Lsp_prev_extract(prev_lsp, buf,
            fg[*prev_ma], freq_prev, fg_sum_inv[*prev_ma]);
        
    }
    Lsp_prev_update(buf, freq_prev);
    return;
}


/*-------------------------------------------------------------------*
 * Function  D_lspe:                                                  *
 *           ~~~~~~                                                  *
 *-------------------------------------------------------------------*/

void D_lspe(
  Word16 prm[],          /* (i)     : indexes of the selected LSP */
  Word16 lsp_q[],        /* (o) Q15 : Quantized LSP parameters    */
  Word16 erase,           /* (i)     : frame erase information     */
  Word16 freq_prev[MA_NP][M],    /* (i/o) Q13 : previous LSP MA vector        */
  Word16 prev_lsp[],            /* (i/o) Q13 : previous LSP vector        */
  Word16 *prev_ma               /* (i/o) previous MA prediction coef.*/

)
{
    Word16 lsf_q[M];       /* domain 0.0<= lsf_q <PI in Q13 */
    
    Lsp_iqua_cse(prm, lsf_q, erase, freq_prev, prev_lsp, prev_ma);
    
    /* Convert LSFs to LSPs */
    Lsf_lsp2(lsf_q, lsp_q, M);
    
    return;
}